Calculating Email Opens

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Act-On tracks email opens using a small tracking pixel embedded in the message, and a fallback based on link clicks for recipients who don't load images. Knowing how opens are counted explains why the numbers sometimes look lower, or higher, than you'd expect from your audience.

Why this matters: Open rates are the metric most people reach for first, and they're also the most misinterpreted. Opens depend on whether images load, whether a recipient uses a preview pane, and whether tracker-blocking extensions are involved. Understanding the mechanics helps you judge what a given open rate really means for your audience.
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  • Opens are tracked via a 1x1 pixel that loads when the email HTML renders.
  • Recipients with images off or plain text view do not register an open unless they also click a link.
  • A click without a pixel load still counts as one open.
  • Preview panes that load images count each preview as an open.
  • Ad and tracker-blocking browser extensions can suppress the pixel in web mail.
Try it like this: If a recipient opens your email once and then clicks 9 links, the Sent Message Report shows 1 open. If the same recipient opens the email 4 times with images disabled and never clicks, it shows 0 opens. If they open once with images off and click 8 times, it shows 1 open, tracked by the click.

How opens are counted

Every HTML email Act-On sends includes a tiny tracking pixel (a 1x1 transparent image). When the recipient's email client loads the image, that request tells Act-On the message was opened. It's the primary way opens are recorded.

Some recipients have images turned off, or use a plain-text view. In those cases, the pixel never loads and no open is recorded by the normal method. However, if the recipient clicks a link in the message, Act-On counts that as an open too, because a click is proof the email was read.

Examples:

  • A recipient opens an email once and clicks 9 times: 1 open.
  • A recipient opens an email 4 times with images disabled and never clicks: 0 opens.
  • A recipient opens an email once with images disabled and clicks 8 times: 1 open.
  • A recipient opens an email 10 times with images loaded and clicks 7 times: 10 opens (Total Opened; Opened shows 1 unique).

Preview panes and extensions

Some email clients show email content in a preview pane before the message is fully opened. If images load in that preview, each preview counts as an open. Microsoft Outlook's preview pane is the most common example.

Note: Ad and tracker-blocking browser extensions can prevent the tracking pixel from loading in web-based mail. If a recipient uses one, they won't register as an open unless they click a link in the message.

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